Seminal research by Steve Chibnall more than 30 years ago on the relationship between the Metropolitan police and crime correspondents concluded that the balance of power was asymmetrically in favour of the police.

The research appeared long before 24-hour news, social media, the growth in corporate communications departments or the police's reaction to the phone-hacking scandal, which exposed overly cosy relationships between officers and News of the World executives.

Two years ago criminologist Rob Mawby revisited Chibnall's work, and warned: "There are reasons to fear for the future ability of crime reporters to provide independent critical reporting on policing and crime … The asymmetric police-media relationship identified by Chibnall therefore endures and has become more pronounced in terms of police dominance of the relationship."

Today, in the aftermath of a scandal which shook Britain's biggest police force to its core, power seems more firmly in the hands of the Met police – or, to be more precise, very senior officers and the management board – than at any time in the past.

There is no doubt that there has been a necessary examination of the framework for conducting police and media relationships as forces react – and sometimes overreact – to the phone-hacking scandal and the Leveson inquiry.

Some within the police service and outside argue that more formalisation and a tightening of control are welcome. Others, including senior police officers, see the benefits of an open and trusting relationship with specialist crime journalists for policing purposes and the public good, and warn against discarding a relationship which has worked to the benefit of the public, the police and the media for decades.

Only a minority of police and journalists are guilty of bad practice, of illegality and corruption. But Scotland Yard is using the scandal to claw back control over the flow of information, to restrict access to detectives and uniformed officers, and to threaten them with criminal and/or disciplinary proceedings if they maintain informal relationships with journalists they have learned to trust.

Officers who talk to crime correspondents to provide context, enhance understanding, guide, give colour and texture or hold an off-the-record conversation to ensure no harm is done by a media report, are under active criminal investigation; a Scotland Yard press officer is facing a disciplinary inquiry for having a coffee with a crime reporter; and officers of middle rank and above describe an authoritarian atmosphere within the Met.

The relationship between the police and crime journalists has always been marked by tension, even with the closest of contacts. The police hold the information and the journalist seeks it. Much of that information is not released into the public domain for operational reasons, or to protect the privacy of individuals and to avoid prejudice to the legal process. But a great deal of information can be released in order to enhance the public's understanding of police work, to show that criminals can and will be caught, to prevent harm to individuals, to expose wrongdoing and corruption, to help hunts for suspects and – in a democratic society – to ensure that our police are as open and transparent as possible.

Yet the new draft guidance issued to officers at Scotland Yard seems designed to put the fear of God into any young detective seeking to speak to a journalist for any of those reasons.

"Assume you are being recorded" is one instruction. And under the headline "personal dealings with the media" – "hospitality taken from journalists should be the exception not the rule and alcohol should play no part".

While shutting off informal contact between crime correspondents and their police contacts, the Yard routinely turns down requests for interviews with senior officers – four to date for this journalist – and chooses instead to use social media to speak to the public.

Regular webchats with the commissioner Bernard Hogan-Howe, however, do not open him up to serious scrutiny and, while many sections of the public continue to distrust the police, there is a need for informed, responsible, independent reporting of crime and policing issues for which journalistic contact with police sources is essential.

Those who do speak out within the police service on bad practice and corruption face a difficult time, and speak of being mistreated and marginalised. Within the Met, the Guardian knows of at least two cases where whistleblowers have been bullied, isolated and investigated for spurious disciplinary offences which have never been proven, after making complaints to superior officers about bad practice, including racism and sexual assault.

"The moment you become a whistleblower the senior management will know about it," said one former Met officer. "They will do everything they can to intimidate and persecute you in order to protect themselves and their career path.

"There is no protection, these people are extremely powerful and the police service is a highly secretive organisation which if it can will choose secrecy over being open." Even simple factual information is routinely withheld. The list is endless but examples include: the attack on German Gorbuntsov was portrayed as a London gangland killing rather than the attempted assassination of a Russian banker; the Met press bureau refused to reveal where the Tetra Pak heir Hans Kristian Rausing was arrested; and it withheld details of the arrest in February of @InspectorWinter, a fraudster posing as a tweeting police officer during the August riots.

Does any of this matter? Two years ago Mawby concluded it did. "This study suggests that we are edging further towards a public sphere dominated by the sectional interests of the powerful and in which crime reporters find it increasingly difficult to make their independent, sometimes dissenting voices heard. If this continues one dimension of the complex framework of police accountability will be further diminished."